OLED Light Extraction via Particle Mask Etching
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Solution Overview
Problem
Existing organic light-emitting diodes (OLEDs) face challenges in achieving high light extraction efficiency across a broad wavelength region, particularly for white light-emitting diodes and those emitting from visible light to near-infrared, due to constant periodic microstructures that are optimized for specific wavelengths, limiting their effectiveness.
Innovation Solution
A method involving a dry etching process using a particle single layer film as a mask to create a substrate with a two-dimensional uneven structure, where the particle film is formed from a mixture of particles with different sizes, ensuring the uneven structure has an average height of 15-150 nm and spectral intensity across a wide wave number range, allowing for efficient light extraction from visible light to near-infrared wavelengths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a constant periodic microstructure is provided on the metal layer surface, then light extraction efficiency is improved at specific wavelengths, but light extraction efficiency deteriorates across broad wavelength regions
Solution Approach 1:
The patent applies local quality by creating non-uniform particle size distribution in the mask film, where different regions have different particle sizes that correspond to different wavelength ranges. This allows each local region to optimize light extraction for specific wavelengths while collectively covering the entire visible and near-infrared spectrum.
Solution Approach 2:
The patent changes the parameter of particle size distribution from uniform to non-uniform. By controlling the standard deviation of particle sizes (σ/D ≥ 0.1), the microstructure can effectively extract light across a broad wavelength range (400-2500 nm) rather than being optimized for a single wavelength.
2Manufacturing precision
If a particle single layer film with narrow size distribution is used as etching mask, then manufacturing precision is improved, but light extraction efficiency across broad spectrum deteriorates
Solution Approach 1:
The patent deliberately changes the particle size distribution parameter from narrow (σ/D < 0.1) to broad (σ/D ≥ 0.1) distribution. This counterintuitive approach sacrifices some manufacturing precision to achieve superior light extraction efficiency across the entire visible and near-infrared spectrum.
Solution Approach 2:
The patent uses local quality by having different particle size regions in the mask film, where each size range corresponds to optimal extraction for specific wavelength bands, collectively providing full spectral coverage.
3Illumination intensity
If average height of uneven structure is increased, then light extraction efficiency is improved, but device thickness increases
Solution Approach 1:
The patent optimizes the average height parameter of the uneven structure to fall within 10-200 nm. This parameter range provides sufficient light extraction efficiency enhancement through surface plasmon resonance while maintaining the thin-film characteristic of OLED devices.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach significantly enhances light extraction efficiency across the entire visible and near-infrared spectrum, improving the brightness and performance of OLEDs in image display and illumination devices by converting near-field light into radiant light through surface plasmon diffraction.
Implementation Method 1
a substrate preparation step of preparing, by a dry etching method using a particle single layer film as an etching mask, a substrate provided with an uneven structure
Implementation Method 2
a method that utilizes surface plasmon resonance... The periodic microstructure formed on the metal layer surface functions as a diffraction grating, converting the surface plasmon into light at the cathode surface
Implementation Method 3
The periodic microstructure formed on the metal layer surface functions as a diffraction grating
Implementation Method 4
a deposition step, on the uneven structure, at least an anode conductive layer, an electroluminescent layer including a light-emitting layer containing an organic light-emitting material, and a cathode conductive layer containing a metal layer
Data Source
Figure 1~2
Figure 3
Figure 4~5
AI summary
A method of manufacturing an organic light-emitting diode of a first aspect includes: a step of preparing, by a dry etching method using a particle single layer film as an etching mask, a substrate provided with an uneven structure in which a plurality of unevenness is arranged in two dimensions on the surface of the substrate, and a step of stacking, on the uneven structure, at least an anode conductive layer, an EL layer including a light-emitting layer containing an organic light-emitting material, and a cathode conductive layer containing a metal layer, such that the uneven structure is reproduced on the surface of the metal layer on the side of the EL layer, wherein the particle mono layer film is formed using a mixture of a plurality of particles having different particle sizes, and an uneven structure is provided which satisfies a requirement (A) that the average height is at least 15 nm but not more than 150 nm, and a requirement (B) that the spectral intensity of the height distribution has a finite value across the entire range in which the absolute value |k| of a wave number is denoted by formula (I) shown below, and the integral value of the spectral intensity across the range accounts for 35% or more of the integral value of the spectral intensity across the entire wave number range. [Mathematical Formula 1] Re2πλmax⋅εmλmax⋅εdλmaxεmλmax+εdλmax≤k≤Re2πλmin⋅εmλmin⋅εdλminεmλmin+εdλmin εm(λ) represents the relative dielectric constant of the metal that constitutes the metal layer. εd(λ) represents the equivalent relative dielectric constant of the EL layer. λmax represents the maximum extracted wavelength, and λmin represents the minimum extracted wavelength. Re[ ] denotes the real part of a complex number.